/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 *
 */


package com.googlecode.protobuf.minarpc;

import java.nio.ByteBuffer;

import org.apache.mina.core.buffer.SimpleBufferAllocator;
import org.apache.mina.core.session.IoSession;
import org.apache.mina.filter.codec.ProtocolEncoderAdapter;
import org.apache.mina.filter.codec.ProtocolEncoderOutput;

import com.google.protobuf.Message;


/**
 * An Apache MINA protocol encoder for encoding a protobuf service response message into a raw binary byte stream 
 *  
 * @author Zhenlei Cai (zcai@gaocan.com)
 * @version $Rev$, $Date$
 */
public class RpcResponseEncoder extends ProtocolEncoderAdapter {

    @Override
    public void encode(IoSession session, Object message, ProtocolEncoderOutput out) throws Exception {
	Message resp = (Message) message;
	SimpleBufferAllocator alloc = new SimpleBufferAllocator();
	byte[] respBytes = resp.toByteArray();
	ByteBuffer respBuf = ByteBuffer.wrap(respBytes);
	// write length as 4 bytes header
	assert (respBytes.length == resp.getSerializedSize());
	ByteBuffer headerBuf = ByteBuffer.allocate(4);
	headerBuf.putInt(respBytes.length);
	headerBuf.flip();
	out.write((new SimpleBufferAllocator()).wrap(headerBuf));
	out.write(alloc.wrap(respBuf));
	
    }
}
